Cannot redeem Peacock for Diamond Members offer

I got an email saying that as a Diamond Member (Xfinity subscriber for over 10 years) I should have access to Peacock Premium for free. This is a great offer and I'd like to use it.

However, when I go to redeem it, both from clicking the "Redeem Peacock" button in the email, and through trying to access "Membership Benefits" directly on the Xfinity website, I get stuck in an endless loop where it kicks me over to this page:

I click "Join now", and then the browser hops back and forth between a few other pages, and then boots me back to this page again with the "Join now" button. I have tried it from every device and browser I have available, including the official Xfinity app. Nothing seems to do the trick. How do I get past this so I can redeem the Peacock offer for Diamond members?

Thanks!